The flavin coenzyme specificity of liver pyridoxine (pyridoxamine) 5'-phosphate will be delineated and an examination of the stereochemical dictates of the substrate reaction made. Chemical syntheses of blocked and unblocked forms of the active- site flavinyl peptide from mitochondrial monoamine oxidase will be completed and a study begun of its spectroscopic properties, especially as they relate to the interaction of the tyrosyl residue adjacent to the 8 alpha-S-cysteinyl flavin within the peptide. Radioactive 8 alpha-N3-histidyl riboflavin, a natural covalently bound form of riboflavin, will be synthesized for an investigation, which will ultimately include its catabolic fate, as well as whether or not it is a biosynthetic prescursor to the 8 alpha-histidyl FAD found within certain enzymes.